CSIS 110 - Lecture 22
Announcements:
Quiz Wednesday.
Read Chapter 5, sections 5.1 to 5.4.
Programming Assignment on course web page
Midterm Grades: 25% Quizzes, 35% HW/Labs, 40% Programs
Random Numbers
In the real world, some things occur randomly, such as: flipping coins, rolling dice,
atomic decay. What are some other situations where randomness occurs or is useful?
- games
- simulations
- controlled experiments
- lottery
We'd like to be able to write programs that can do these sorts of things, but the programs
must have a source of random behavior. So far, every program we have seen does the
same thing every time it is run if it starts with the same data.
Java includes a class named Random. Let's go look it up.
Open BlueJ – go look it up in the Java documentation. (Help | Java Class Libraries ).
What package is it contained in? (That is, where do you need to tell Java to look for the
Random class in an import statement?)
How do you create an instance of a Random?
How do you generate a random number?
- create an instance of class Random
- call a method on that object to get a number
Open the random project (in chapter 5 directory). Go ahead and play around with it.
What do the methods do?
What is the difference between the two versions of printTenRandoms?
Let's look at the code in a little more detail…
Instance variable: a Random number generator
Constructor: Initialize the Random number generator
